There are a large number of conventional halogenated products that are available for use in flame retardancy in polymeric systems. These materials are petroleum based. Some such materials have been used in polyurethane foams as disclosed by E. D. Weil and S. V. Levchik, Fire Retardancy of Polymeric Materials, edited by Arthur F. Grand and Charles A. Wilkie, Marcel Dekker, Inc., 2000, page 572.
These include commercially available flame retardants for flexible polyurethane that includes both chlorinated and brominated derivatives that may include reactive hydroxyl, amine and anhydride groups.
Natural oils are the triglycerides of saturated and unsaturated fatty acids from plants and animal fats and microorganisms.
Natural oil hydroxylates included chemically unmodified and modified natural oil molecules that contain hydroxyl groups. Such compounds are either pure fatty acid derivatives or the mixtures of these fatty acid derivatives that contain triglycerides, diglycerides, monoglycerides, and their oligomerized varieties. Examples of natural oil hydroxylates include naturally existing natural oil that contains hydroxy groups such as castor oil; and the products of fatty acids and polyhydric alcohols with the structure of monoglycerides, diglycerides, and triglycerides. Examples of natural oil hydroxylates also include the products that chemical modified with by means of epoxidation, transesterification, alcoholysis, aminolysis, ozonolysis, hydrolysis, alkoxylation, and hydroformation to generate hydroxy groups. Examples of such process have been descrivbed in the prior art such as, for example, U.S. Pat. Nos. 6,686,435, 6,107,433, U.S. 2006/0041156, and WO2006/020965 or as described in the following technical publication: L. L. Monteavaro, E. O. da Silva, A. P. O. Costa, D. Samios, A. E. Gerbase, C. Petzhold, Polyurethane Networks from Formiated Soy Polyols: synthesis and Mechanical Characterization, JAOCS (2005), 82: 365-371; A. Guo, I. Javni, Z. Petrovic, J. Appl. Poly. Sci. (2000), 77: 467-473;A. Zlatanic, C. Lava, W. Zhang, X. S. Petrovic, J. Poly. Sci.: Part B: Polymer Physics (2004), 42: 809-819; A. Guo, I. Vavni, Z. Petrovic, Rigid Polyurethane Foams Based on Soybean Oil, J. Appl. Poly. Sci (2000), 77: 467-473
The halogenated anhydrides or their corresponding alkyl esters that are useful for the present invention are those, for example, halogenated maleic anhydride, halogenated phthalic anhydride, 2,3-dichloromaleic anhydride, 2,3-dibromaleic anhydride, dichlorophthalic anhydride, 4-chloro-1,8-nathalic anhydride, chlorophathalic anhydride, dichlorophathalic anhydride,
Examples of brominated products include tetrabromophthalic anhydride, tetra bromophthalate diol, tetrabromobenzoate esters and dibromoneopentyl glycol, pentabromodiphenyl oxide, tribromonepentyl alcohol, decabromodiphenyl oxide, bis(tribromophenoxyl)ethane, hexabromocyclododecane, and chlorinated paraffins, and the like.
Most of these materials are of relatively low molecular weight with limited compatibility with polymer matrices and are made with the use of petroleum based raw materials.
Attempts were made in the past to produce halogenated compounds based on castor oil and/or ricinoleic esters as disclosed in U.S. Pat. No. 3,732,265 that issued in 1973 to Roth and Hills. The compounds were synthesized by reacting castor oil and/or ricinoleic ester and aliphatic haloepoxide for non-rigid polyurethane foams. This is a different approach from the present invention and the application of this compound is only for non-rigid foams.
Attempts were made in the past to synthesize halogenated compounds based on soybean oil as disclosed in Andrew Guo, Youngjin Cho, Zoran S. Petrovic, Structure and Properties of Halogenated and Non-halogenated Soy Based Polyols, Journal of Polymer Science: Part A Polymer Chemistry, 38, 3900 to 3910 (2000) and Zoran S. Petrovic, Andrew Guo, Wei Zhang, Structure and Properties of Polyurethanes Based on Halogenated and Non-halogenated Soy-based Polyols. Journal of Polymer Science: Part A Polymer Chemistry, 38, 4062-4069 (2000).
The compounds were synthesized by reacting epoxidized soybean oil with hydrochloric or hydrobromic acid in a solvent. The resulting chlorinated and brominated derivatives were characterized as having equivalent weights of 285 and 308, hydroxyl numbers of 197 and 182, a functionality of 3.8 and 4.1, and a halogen content of 12.43 and 25.33, respectively. The brominated compound was thermally unstable.
Using a natural oil based matrix of higher molecular weight results in reduced migration of the flame retardant, and allows for increased compatibility of the flame retardant with a polymer without detrimentally affecting the mechanical properties of the polymer.